Search for banned gases
Recent detective work by scientists in the UK and Germany could make it possible to identify the sources of banned chlorofluorocarbons that are probably still being released into the atmosphere - and ruining the planet. Using mass spectrometers, the researchers at the universities of East Anglia and Frankfurt analysed air samples collected in the stratosphere by balloons belonging to the French space agency, the Centre National d'Etudes Spatiales.
Right atmosphere: in a simulated stratosphere laboratory, Dr Jan Kaiser (right) and BSc student Martin Martin work to identify the sources of banned chlorofluorocarbons damaging the ozone layer that protects life on Earth. (Image by University of East Anglia)
They discovered the largest chlorine isotope enrichment ever found in nature. The use of chlorofluorocarbons (CFCs) has been banned in most countries because of their depletion of the ozone layer that absorbs 97-99 per cent of the sun's high-frequency ultraviolet light that is potentially damaging to life on Earth. Because of their long lifetimes, the CFCs' atmospheric concentrations are expected to decline only slowly. But the observed decline is even slower than scientists predicted. The likely reasons for this are the continued use of CFCs and emissions from old refrigerators, air conditioning units and waste disposal.
"We are particularly excited by this discovery because this is a totally new observation for atmospheric chlorine," said Johannes Laube, of the University of East Anglia's School of Environmental Sciences.
"Potentially, the technique we developed could enable us to identify remaining sources of CFCs in the atmosphere and to measure human contributions to naturally occurring ozone-depleting gases."
The measurements were obtained from samples brought back by the space balloons; the research group has started experiments in a laboratory where they replicate the reactions above the planet.
"We try to measure the isotope effect in our laboratory in simulated stratospheric conditions," said Dr Jan Kaiser, also of the School of Environmental Sciences.
"We do need to do more method development work and gather additional information before we can identify the fingerprint of the isotope in this way - but this discovery opens the door to that possibility," he added.
Much of the modern lifestyle of the second half of the 20th
century has been made possible by the use of CFCs. CFCs were widely used as coolants in refrigeration and air conditioners, as solvents in cleaners, particularly for electronic circuit boards, as a blowing agent in the production of foam (for example: fire extinguishers) and as propellants in aerosols. Man-made CFCs have been named as the main cause of stratospheric ozone depletion. They are estimated to have a lifetime in the atmosphere of about 20 to 100 years and, consequently, one free chlorine atom from a CFC molecule can do a lot of damage, destroying ozone molecules for a long time. Although emissions of CFCs around the developed world have largely ceased because of international control agreements, following the discovery of the Antarctic ozone hole in 1985, the damage to the stratospheric ozone layer will continue well into the 21st